Light-emitting apparatus capable of adjusting a color of a projected light thereof

ABSTRACT

A light-emitting apparatus includes a light source to emit light, a photonic crystal to pass light of different wavelengths based on the light from the light source, and a projector to project the light passing through the photonic crystal. The photonic crystal may be electrically or mechanically controlled to pass the different wavelengths of light.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No.10-2012-0129098, filed on Nov. 14, 2012, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND

1. Field

The present disclosure relates to light-emitting apparatuses foradjusting a color of projected light.

2. Description of the Related Art

Recently, an input apparatus using an electric pen has been developedand used in various fields. When a user draws a character, a number, oran image with the electric pen, a sensor or a receiver which mayrecognize the electric pen may input data desired by the user to anapparatus such as a computer or a mobile device. Such a device maytherefore replace or supplement the use of a keyboard or mouse.

Other types of pens have also been developed as input devices. Examplesinclude an optical pen which uses a laser or a light emitting diode(LED), and a digital pen which detects distance based on an ultra soundsignal or an infrared light.

Input pens, therefore, allow a user to input data just as though theuser were using an actual pen. However, there are drawbacks to existingpens. For example, in order to change the color of an image or thethickness of a line using existing pens, a menu needs to be used. Morespecifically, a user has to use the pen to access and then makeselections within different menus of an application program in order toset the color of an image and or the thickness of a line. And, if thecolor or line thickness has to be changed, the menu needs to be accessedagain.

SUMMARY

In accordance with example embodiments, a light-emitting apparatus isprovided to allow a user to freely select and project light of a desiredcolor. In accordance with one example embodiment, a light-emittingapparatus comprising: a light source configured to emit light; aphotonic crystal configured to pass light of different wavelengths basedon the light emitted from the light source; and a projector configuredto project the light which passes through the photonic crystal, thephotonic crystal configured to be electrically controlled to pass thedifferent wavelengths of light.

The light-emitting apparatus may further include an aperture configuredto control a beam diameter of the projected light; a controllerconfigured to control operation of at least one of the photonic crystalor the aperture; and a input device configured to receive a command tobe sent to the controller.

The photonic crystal and the aperture may be arranged along an opticalaxis between the light source and the projector.

The apparatus may further comprise a first transparent electrode coupledto a light incident surface of the photonic crystal; and a secondtransparent electrode coupled to a light emission surface of thephotonic crystal, wherein a first voltage difference between the firstand second transparent electrodes corresponds to a first wavelength ofthe different wavelengths of light, and a second voltage differencebetween the first and second transparent electrodes corresponds to asecond wavelength of the different wavelengths of light.

The photonic crystal may include a colloid solvent and a plurality ofphotonic crystal particles arranged within the colloid solvent in aperiodic structure, and the photonic crystal particles have a surfacewhich is electrically charged such that a repulsive force is appliedtherebetween. The photonic crystal particles may comprise particles ofsilica, polymethylmethacrylate (PMMA), poly-n-butylmethacrylate (PBMA),or copolymer thereof.

The photonic crystal may comprise a transparent polymer which contractsor expands based on the first and second voltage differencesrespectively; and a plurality of photonic crystal particles arrangedwithin the transparent polymer in a periodic structure.

In accordance with another embodiment, a light-emitting apparatuscomprises a light source configured to emit light; a photonic crystalconfigured to pass light of different wavelengths based on the lightemitted from the light source; a projector configured to project thelight which passes through the photonic crystal; and a deflectorconfigured to apply a pressure to cause the photonic crystal to changebetween contracted and expanded states, the photonic crystal having aphotonic bandgap which varies according to the contracted and expandedstates of the photonic crystal, the photonic crystal configured tooutput a first wavelength of the different wavelengths in the contractedstate and configured to output a second wavelength of the differentwavelengths in the expanded state.

The apparatus may further comprise an aperture configured to adjust abeam diameter of the projected light; a controller configured to controloperation of the aperture; and an input device configured to receive acommand to be sent to the controller. The aperture and the photoniccrystal may be sequentially arranged along an optical axis between thelight source and the projector.

The deflector may comprise a first surface configured to press thephotonic crystal; a second surface configured to prevent movement of thephotonic crystal in a direction of an optical axis; and a third surfaceconfigured to prevent movement of the photonic crystal in a directioncrossing the optical axis.

The apparatus may further include a case, wherein the first surface hasa portion which protrudes outwardly from the case to contact an externalobject and configured to slide in forward and backward directions withrespect to the case, and wherein, when the first surface contacts theexternal object, the first surface presses against the photonic crystalto cause the photonic crystal to pass from the expanded state to thecontracted state.

The photonic crystal may comprise a transparent elastic material whichchanges between the contracted state and the expanded state based on apressure; and a plurality of photonic crystal particles arranged withinthe transparent elastic material at a periodic structure.

In accordance with another embodiment, a light-emitting apparatuscomprises a light source configured to emit light; a photonic crystalconfigured to reflect light of different wavelengths based on the lightemitted from the light source; a projector configured to project thelight reflected by the photonic crystal; and a light guide disposedbetween the photonic crystal and the projector to transmit light emittedfrom the light source to the photonic crystal and to transmit the lightreflected by the photonic crystal to the projector, the photonic crystalhaving a variable photonic bandgap which is electrically controlled toadjust the wavelength of the reflected light.

The apparatus may further comprise an aperture configured to adjust abeam diameter of the projected light; a controller configured to controloperation of at least one of the photonic crystal or the aperture; andan input device configured to receive a command to be transmitted to thecontroller.

The photonic crystal, the aperture, the light guide, and the opticalsystem may be sequentially arranged along an optical axis, and the lightsource may be offset from the optical axis and disposed toward anentrance to the light guide.

The apparatus may further comprise a beam splitter disposed at anentrance to the light guide, wherein the beam splitter is configured toreflect light emitted from the light source toward the photonic crystaland to pass the light reflected by the photonic crystal.

The apparatus may further comprise a first transparent electrodedisposed on a light incident surface of the photonic crystal, and asecond transparent electrode disposed on a light emission surface of thephotonic crystal.

The photonic crystal may include a colloid solvent, and plurality ofphotonic crystal particles arranged within the colloid solvent in aperiodic structure, the photonic crystal particles having a surfacewhich is electrically charged such that a repulsive force is appliedtherebetween. The photonic crystal particles comprise particles ofsilica, polymethylmethacrylate (PMMA), poly-n-butylmethacrylate (PBMA),or copolymer thereof.

The photonic crystal may comprise a transparent polymer which expandsand contracts based on electrical stimulus; and a plurality of photoniccrystal particles arranged within the transparent polymer in a periodicstructure.

In accordance with another embodiment, a light-emitting apparatuscomprises a light source configured to emit light; a photonic crystalconfigured to reflect light of different wavelengths based on the lightemitted from the light source; a projector configured to project thelight reflected by the photonic crystal; and a deflector configured toapply pressure for causing the photonic crystal to change betweencontracted and expanded states, the photonic crystal having a photonicbandgap which varies in the contracted and expanded states to adjust thewavelength of the reflected light.

The apparatus may further comprise an aperture configured to control abeam diameter of the projected light; a controller configured to controloperation of at least one of the photonic crystal or the aperture; andan input device configured to receive a command to be sent to thecontroller.

The deflector may comprise a first surface configured to press thephotonic crystal; a second surface configured to prevent movement of thephotonic crystal in a direction of an optical axis; and a third surfaceconfigured to prevent movement of the photonic crystal in a directioncrossing to the optical axis.

The apparatus may further comprise a case, wherein the first surface hasa portion which protrudes outwardly from the case to contact an externalobject and is configured to slide forward and backward with respect tothe case, and wherein, when the first surface slides in the backwarddirection, the first surface presses against the photonic crystal.

The first surface may have a cylinder shape or a polygonal tube shape,and the light source and aperture are disposed adjacent the firstsurface.

The photonic crystal may comprise a transparent elastic material whichchanges between expanded and contracts states based on an pressure; anda plurality of photonic crystal particles arranged within thetransparent elastic material at a periodic structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of example embodiments willbecome more apparent by describing in detail example embodiments withreference to the attached drawings. The accompanying drawings areintended to depict example embodiments and should not be interpreted tolimit the intended scope of the claims. The accompanying drawings arenot to be considered as drawn to scale unless explicitly noted.

FIG. 1 is a schematic view illustrating an embodiment of alight-emitting apparatus.

FIGS. 2A and 2B illustrate examples of the structure and operation of atransmissive photonic crystal shown in FIG. 1 according to oneembodiment.

FIGS. 3A and 3B illustrate examples of the structure and operation of atransmissive photonic crystal shown in FIG. 1 according to anotherembodiment.

FIG. 4 is a schematic view illustrating the structure of alight-emitting apparatus according to another embodiment.

FIGS. 5A and 5B illustrate an example of the structure and operation ofa transmissive photonic crystal shown in FIG. 4.

FIG. 6 is a schematic view illustrating a structure of a light-emittingapparatus according to another embodiment.

FIG. 7 is a schematic view illustrating a structure of a light-emittingapparatus according to another embodiment.

FIG. 8 is a schematic view illustrating a structure of a light-emittingapparatus according to another embodiment.

DETAILED DESCRIPTION

Detailed example embodiments are disclosed herein. However, specificstructural and functional details disclosed herein are merelyrepresentative for purposes of describing example embodiments. Exampleembodiments may, however, be embodied in many alternate forms and shouldnot be construed as limited to only the embodiments set forth herein.

Accordingly, while example embodiments are capable of variousmodifications and alternative forms, embodiments thereof are shown byway of example in the drawings and will herein be described in detail.It should be understood, however, that there is no intent to limitexample embodiments to the particular forms disclosed, but to thecontrary, example embodiments are to cover all modifications,equivalents, and alternatives falling within the scope of exampleembodiments. Like numbers refer to like elements throughout thedescription of the figures.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of example embodiments. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it may be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between” versus “directly between”, “adjacent” versus “directlyadjacent”, etc.).

In the drawings, it is understood that the thicknesses of layers andregions may be exaggerated for clarity. It will also be understood thatwhen a layer is referred to as being “on” another layer or substrate, itcan be directly on the other layer or substrate or intervening layersmay also be present. Like reference numerals in the drawings denote likeelements, and thus their description will not be repeated. As usedherein, the term “and/or” includes any and all combinations of one ormore of the associated listed items. Expressions such as “at least oneof,” when preceding a list of elements, modify the entire list ofelements and do not modify the individual elements of the list.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises”, “comprising,”, “includes” and/or “including”, when usedherein, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

It should also be noted that in some alternative implementations, thefunctions/acts noted may occur out of the order noted in the figures.For example, two figures shown in succession may in fact be executedsubstantially concurrently or may sometimes be executed in the reverseorder, depending upon the functionality/acts involved

Hereinafter, a light-emitting apparatus capable of adjusting light ofprojected light will be described in detail with reference to theaccompanying drawings. In the drawings, like reference numerals refer tolike elements throughout, and for illustrative and clarificationpurposes, respective elements in the drawings may be exaggerated insize. Also, exemplary embodiments described herein are given forillustrative purposes only and various modifications thereof may bemade. Further, in a layered structure described herein, the term “upperportion” or “upper” should be understood as including not only oneelement contacting and directly being on the other element but also oneelement being above the other element without contacting the otherelement.

FIG. 1 is a schematic view illustrating an example embodiment of a lightemitting apparatus 10. In this example, the light-emitting apparatusincludes a transmissive photonic crystal which may be electricallycontrolled.

Referring to FIG. 1, the light-emitting apparatus 10 includes a lightsource 12 emitting a white light, a filter in the form of an photoniccrystal 13 passing only light of a predetermined wavelength of the whitelight, and an optical system 17 projecting the light which passesthrough the photonic crystal 13 toward an external surface. The photoniccrystal 13 may change a photonic bandgap according to an electricalcontrol signal to adjust a wavelength of projected light.

In addition to these features, the light-emitting apparatus 10 mayinclude an aperture 14 for adjusting a beam diameter of the projectedlight, and a controller 15 for controlling an operation of the photoniccrystal 13 and the aperture 14 according to a user command. Thelight-emitting apparatus 10 may further include one or more controlbuttons and/or a control panel 16 for receiving a user command andtransmitting the user command to the controller 15. The controlbutton(s) may, for example, be pressed to toggle or otherwise switchbetween multiple colors to be output.

In addition, the light-emitting apparatus 10 may include a case 11 inwhich the light source 12, the photonic crystal 13, the aperture 14, andthe controller 15 are located within an internal space of the case 11.

One or more control button(s), a control panel 16 or another type ofinput device and an optical system 17 or projector may be disposed on anexternal surface of the case 11. For example, the light source 12 andthe optical system 17 may be disposed at opposing ends of the case 11,respectively, along a direction of an optical axis. Also, the photoniccrystal 13 and the aperture 14 may be disposed along a direction of anoptical axis between the light source 12 and the optical system 17 orprojector. Although it is shown in FIG. 1 that the aperture 14 isdisposed between the photonic crystal 13 and the optical system 17, inalternative embodiments the aperture 14 may be disposed between thelight source 12 and the photonic crystal 13. The optical system 17 orprojector may include one or more lens, prisms, or other light-adjustingelements for directing or otherwise adjusting the output light.

The light source 12 may emit white light including all spectrums of thevisible light region and, for example, a light-emitting diode (LED) or alaser diode (LD) may be used as the light source 12. The white lightemitted from the light source 12 may pass through the photonic crystal13, may be adjusted in terms of its beam diameter by the aperture 14,and may be projected outside the pen through the optical system 17.

The photonic bandgap of the photonic crystal 13 may be electrically andcontinuously controlled according to an electrical signal provided bythe controller 15. According to the photonic bandgap of the photoniccrystal 13, a wavelength (i.e., color) of the projected light may bedetermined. For example, of the white light which is incident on thephotonic crystal 13, only a portion of light having a color such as red,green or blue may pass through the photonic crystal 13 according tocontrol of the controller 15. Therefore, a user may freely select acolor and a beam diameter of the projected light through the controlpanel 16.

In accordance with an example embodiment, the photonic crystal 13 maycorrespond to an artificial crystal formed, for example, by regularlyarranging two or more different materials having different refractiveindexes in a two-dimensional or a three-dimensional manner. When thephotonic crystal 13 has a regular lattice structure, the photoniccrystal 13 may have a photonic bandgap that sufficiently blocks orpasses light having a desired wavelength due to periodic distribution ofa refractive index.

The photonic bandgap of the photonic crystal 13 may vary according to arefractive index and a periodic structure of materials constituting thephotonic crystal 13. Therefore, by electrically modifying the periodicstructure of the photonic crystal 13, it is possible to adjust thephotonic bandgap of the photonic crystal 13.

FIGS. 2A and 2B illustrate an exemplary structure and operation of thetransmissive photonic crystal 13 shown in FIG. 1 according to an exampleembodiment. Referring to FIGS. 2A and 2B, the photonic crystal 13 mayinclude a colloid solvent 24 and photonic crystal particles 23distributed within the colloid solvent 24. For example, the colloidsolvent 24 may include an inorganic solvent such as water.

Additionally, or alternatively, the photonic crystal particle 23 may bea nano-size particle having an electrically charged surface. Thephotonic crystal particle 23 may be manufactured, for example, byapplying an electric stimulus to a metal particle, or alternatively thephotonic crystal particle 23 may be manufactured by using a polarizedmaterial which polarizes itself on a surface thereof. According to oneembodiment, a zeta potential of about −70 mV may be naturally generatedon a surface of a polystyrene nano-size particle having a diameter ofabout 135 nm.

The photonic crystal particles 23 having a surface which is electricallycharged are arranged by themselves due to a repulsive force between themwithin the colloid solvent 24. As a result, the charged photonic crystalparticles 23 within the colloid solvent 24, may be arranged in aperiodic structure at a regular interval. Due to such a periodicstructure, the colloid solvent 24 and the photonic crystal particles 23distributed within the colloid solvent 24 may have a characteristic ofthe photonic crystal.

The photonic bandgap of the photonic crystal 13, including the colloidsolvent 24 and the photonic crystal particles 23, may be determinedaccording to a refractive index of the colloid solvent 24, a refractiveindex of the photonic crystal particle 23, and/or a size and a densityof the photonic crystal particle 23.

For example, when water is used as the colloid solvent 24 andpolystyrene particles having a diameter of about 100 nm to 500 nm areused as the photonic crystal particles 23, the photonic crystal 13 maybe formed which passes a certain type (e.g., wavelength or color) oflight and reflects other types (colors or wavelengths) of light in thevisible light region. In one example arrangement, a volume ratio of eachphotonic crystal particle 23 may lie in a range of about 5 vol. % to 50vol. %. In alternative embodiments, instead of polystyrene particles,silica, polymethylmethacrylate (PMMA), poly-n-butylmethacrylate (PBMA),and/or copolymer particles may be used as the photonic crystal particles23.

Also, because the photonic crystal particles 23 are electricallycharged, it is possible to adjust the photonic bandgap of the photoniccrystal by modifying an interval between the photonic crystal particles23. This may be accomplished by applying an electrical field to thephotonic crystal 13.

For example, as shown in FIGS. 2A and 2B, transparent electrodes 21 and22 may be disposed on a light incident surface and a light emissionsurface of the photonic crystal 13 respectively, and a voltage appliedto the transparent electrodes 21 and 22 may be adjusted. When thevoltage between the transparent electrodes 21 and 22 is increased,photonic crystal particles 23 which are charged with a negative chargeare drawn more toward a positive electrode. Alternatively, photoniccrystal particles 23 which are charged with a positive charge are drawnmore toward a negative electrode when the voltage is applied. As aresult, a periodic interval between the photonic crystal particles 23may be reduced, to thereby filter the color or wavelength of light fromthe photonic crystal.

More specifically, as shown in FIG. 2A, the voltage difference betweenthe transparent electrodes 21 and 22 may be adjusted to apply anelectric field E1 to the photonic crystal 13. Based on this voltagedifference (which, for example, may be generated by applying a voltageof a certain level to one or both of transparent electrodes 21 and 22),the photonic crystal particles 23 are rearranged within the colloidsolvent 24 such that, for example, only light of a red wavelength maypass the photonic crystal 13.

As shown in FIG. 2B, the voltage difference between the transparentelectrodes 21 and 22 may be adjusted to apply an electrical field E2 tothe photonic crystal 13. Based on this voltage difference, the intervalbetween the photonic crystal particles 23 within the colloid solvent 24may be changed due to the electric field of E2 such that, for example,only light of a blue wavelength may pass the photonic crystal 13.

FIGS. 3A and 3B illustrate an exemplary structure and operation of thetransmissive photonic crystal 13 shown in FIG. 1 according to anotherembodiment. Referring to FIGS. 3A and 3B, the photonic crystal 13 mayinclude a transparent polymer 25 which is elastic and a plurality ofphotonic crystal particles 23 distributed within the transparent polymer25. The photonic crystal particle 23 may be disposed and fixed withinthe transparent polymer 25 at a certain interval or period. Unlike theprevious embodiment, in this embodiment the photonic crystal partiesmove based on the changing elasticity of polymer 25.

More specifically, transparent polymer 25 may be composed of a materialthat expands and contracts based on an electrical stimulus. For example,the polymer material may include cross-linked poly (ferrocenylsilane)and substituents thereof, dielectric elastomer such as acrylicelastomer, silicon elastomer, or fluorine rubber, electrostrictivepolymer such as polyvinylidene fluoride (PVDF), or block copolymer suchas polystyrene-polvinylpyridine (PS-PVP).

In the case of the photonic crystal 13 shown in FIGS. 3A and 3B, whenthe transparent polymer 25 contracts or expands by electrical stimulus,the interval between the photonic crystal particles 23 (which aredistributed and buried in the transparent polymer 25) changes. As aresult, it is possible to adjust the photonic bandgap of the photoniccrystal 13.

For example, as shown in FIGS. 3A and 3B, transparent electrodes 21 and22 may be disposed on the light incident surface and the light emissionsurface of the photonic crystal 13 respectively. When a voltagedifference is applied between transparent electrodes 21 and 22 (e.g., byapplying voltages to one or more of electrodes 21 and 22), the photonicbandgap of crystal 13 may be adjusted.

As shown in FIG. 3A, when a voltage difference between transparentelectrodes 21 and 22 is adjusted such that the electrical field E1 isapplied to the photonic crystal 13, the transparent polymer 25 expandsand only light of a red wavelength may pass through the photonic crystal13. As shown in FIG. 3B, when a voltage difference between thetransparent electrodes 21 and 22 is adjusted such that the electricalfield E2 is applied to the photonic crystal 13, the transparent polymer25 contracts and only light of a blue wavelength may pass through thephotonic crystal 13.

FIG. 4 is a conceptual view illustrating a schematic structure of alight-emitting apparatus 20 according to another embodiment. In thisembodiment, an example of a light-emitting apparatus is discussed whichincludes a transmissive photonic crystal that is mechanicallycontrolled.

Referring to FIG. 4, the light-emitting apparatus 20 includes the lightsource 12 emitting white light, the photonic crystal 13 passing onlylight having a predetermined wavelength of the white light, the opticalsystem 17 projecting the light which passes through the photonic crystal13 toward the outside, the aperture 14 for adjusting the beam diameterof the projected light, the controller 15 controlling the operation ofthe aperture 14, the control panel 16 for receiving a user command to betransmitted to the controller 15, and pressing members 18 a, 18 b, and18 c for elastically contracting or expanding the photonic crystal 13.

Also, the light-emitting apparatus 20 may include the case 11 in whichthe light source 12, the photonic crystal 13, the aperture 14, and thecontroller 15 may be fixed within an internal space of the case 11.Also, the control button(s), panel 16, or another type of input deviceand the optical system 17 may be disposed output or on an externalsurface of the case 11. For example, the light source 12 and the opticalsystem 17 may be disposed on opposing ends of the case 11, respectively,along the direction of the optical axis, and the aperture 14 and thephotonic crystal 13 may be disposed in left-to-right order along thedirection of the optical axis between the light source 12 and theoptical system 17.

Also, the pressing members 18 a, 18 b, and 18 c may be disposed withinand/or on the case 11 to support the optical system 17 and the photoniccrystal 13. According to one possible arrangement, the pressing members18 a, 18 b, and 18 c may include a first pressing member 18 a which isdisposed to partially contact the light emission surface of the photoniccrystal 13 to press the photonic crystal 13 and a second and a thirdpressing members 18 b and 18 c for fixing and supporting the photoniccrystal 13 such that the photonic crystal 13 may not be deviated fromthe optical axis.

The first pressing member 18 a may be formed in a cylinder shape or apolygonal tube shape in which the optical system 17 may be disposedinside. Also, the first pressing member 18 a may have a portion whichprotrudes outwardly from the case 11 and may be configured to beslidable forward and backward with respect to the case 11.

The second pressing member 18 b is fixed within the case 11 and performsa role of supporting the photonic crystal 13 to not move in the opticalaxis direction. Also, the second pressing member 18 b may be formed as atransparent material or a flat panel having an opening formed in acentral portion thereof such that light may pass therethrough, or may bea plurality of supports fixed between an internal wall of the case 11and the photonic crystal 13.

The third pressing member 18 c performs a role of supporting thephotonic crystal 13 to not move in a direction perpendicular to theoptical axis and may be configured to surround at least a part of alateral side of the photonic crystal 13. In one embodiment, the secondpressing member 18 b and the third pressing member 18 c may beintegrally formed. In other embodiments, members 18 b and 18 c areseparately provided.

FIGS. 5A and 5B illustrate an example of the structure and operation ofthe transmissive photonic crystal 13 shown in FIG. 4. Referring to FIGS.5A and 5B, the photonic crystal 13 may include a transparent elasticmaterial 26 and a plurality of photonic crystal particles 23 distributedwithin the transparent elastic material 26. The photonic crystalparticles 23 may be disposed and fixed at a periodic interval within thetransparent elastic material 26.

One type of the transparent elastic material 26 includes a transparentpolymer material which contracts by external pressure and is elasticallyrecovered when an external force is removed. Other examples of thetransparent elastic material 26 include poly dimethylsiloxane (PDMS),block copolymer of poly styrene (PS)-poly vinyl pyrrolidone (PVP),cross-linked acryl polymer such as ethoxylated trimethyloppropanetriacrylate.

Transparent substrates 27 and 28 may be respectively disposed on thelight incident surface and the light emission surface of the photoniccrystal 13 such that the light incident surface and the light emissionsurface of the photonic crystal 13 may not be modified.

Under this structure, when the user does not contact and press the firstpressing member 18 a (which protrudes from the case 11 of thelight-emitting apparatus 20) against an external object such as, forexample, a light-sensing board, the photonic crystal 13 does notcontract as shown in FIG. 5A. In this case, only the light of a redwavelength of the light emitted from the light source 12 may passthrough the photonic crystal 13.

When the user presses the first pressing member 18 a against an externalobject, the first pressing member 18 a deflects to press against atleast a portion of the light emission surface of the photonic crystal13. As a result, the photonic crystal 13 contracts as shown in FIG. 5B.This contraction changes the interval between the photonic crystalparticles 23 within the photonic crystal 13, to thereby change thephotonic bandgap of the photonic crystal 13. When this occurs, thephotonic crystal 13, for example, passes only light in the bluewavelength band.

Therefore, in the light-emitting apparatus 20, the user may adjust thecolor of the light projected from the light-emitting apparatus 20 byadjusting or applying a force against the first pressing member 18 awhen pressed against a light-sensing board or other surface. Also, thebeam diameter of the projected light may be adjusted by the controlpanel 16. The one or more pressing members described herein may bereferred to as deflectors.

In previously described embodiments, examples of the light-emittingapparatuses 10 and 20 for adjusting the color of light passing throughthe photonic crystal 13 have been described. In these embodiments, thephotonic crystal 13 may transmit, block, or reflect light of apredetermined wavelength according to the photonic bandgap thereof, andthus it is possible to implement a light-emitting apparatus that adjuststhe color of the light reflected from the photonic crystal 13.

FIG. 6 is a conceptual view illustrating a schematic structure of alight-emitting apparatus 30 according to another embodiment whichincludes a reflective photonic crystal which is electrically controlled.

Referring to FIG. 6, the light-emitting apparatus 30 includes the lightsource 12 emitting white light, a photonic crystal 33 reflecting onlylight having a certain wavelength of the white light, the optical system17 projecting the light which passes through the photonic crystal 33toward an outside surface, and a light guide 32 disposed between thephotonic crystal 33 and the optical system 17 to transmit light emittedfrom the light source 12 to the photonic crystal 33 and transmit lightreflected from the photonic crystal 33 to the optical system 17. Thephotonic crystal 33 may adjust a wavelength of the reflected light bychanging the photonic bandgap thereof according to an electricalcontrol.

Also, the light-emitting apparatus 30 includes the aperture 14 foradjusting the beam diameter of the projected light, the controller 15controlling the operation of the photonic crystal 13 and the aperture14, and the control panel 16 for receiving a user command andtransmitting the user command to the controller 15. For example, theaperture 14 may be disposed between the photonic crystal 33 and thelight guide 32.

The light-emitting apparatus 30 may further include the case 11, whereinthe light source 12, the photonic crystal 33, the aperture 14, thecontroller 15, and the light guide 32 may be fixed within the internalspace of the case 11, and the control panel 16 and the optical system 17may be disposed on the external surface of the case 11. For example, thephotonic crystal 33, the aperture 14, the light guide 32, and theoptical system 17 may be, as shown in FIG. 6, sequentially disposedalong the optical axis direction.

The light source 12 may deviate from the light axis and may be disposedtoward an entrance to the light guide 32. At the entrance to the lightguide 32, for example, a beam splitter 31 may be disposed. Therefore,the light emitted from the light source 12 may be reflected by the beamsplitter 31 and be incident on the photonic crystal 33.

The photonic crystal 33 may reflect only light having a predeterminedwavelength selected by the user as the photonic bandgap is changedaccording to an electric control. For example, the structure of thephotonic crystal 13 described in FIG. 2A and FIG. 3B may be applied tothis exemplary embodiment, but only the photonic bandgap may be changedto reflect only the light in the visible light region. The lightreflected from the photonic crystal 33 passes through the aperture 14,passes through the beam splitter 31, and then proceeds within the lightguide 32.

Next, the light may arrive at the optical system 17 through an exit ofthe light guide 32 and may be projected toward the outside by theoptical system 17. The beam splitter 31 may be, for example, atransflective mirror or a polarized beam splitter which reflects lightin a polarized direction and passes light in other polarized directions.

FIG. 7 is a schematic view illustrating a structure of a light-emittingapparatus 40 according to another embodiment which includes a reflectivephotonic crystal that is mechanically controlled.

Referring to FIG. 7, the light-emitting apparatus 40 includes the lightsource 12 emitting white light, the photonic crystal 33 reflecting onlylight having a certain wavelength of the white light, the optical system17 projecting the light reflected by the photonic crystal 33 toward theoutside, the aperture 14 for controlling a beam diameter of theprojected light, the controller 15 controlling the operation of theaperture 14, and the control button(s) or panel 16 transmitting a usercommand to the controller 15. The apparatus 40 also includes pressingmembers 38 a, 38 b, and 38 c for elastically contracting or expandingthe photonic crystal 33.

The light-emitting apparatus 40 may further include the case 11 in whichthe light source 12, the photonic crystal 33, the aperture 14, and thecontroller 15 are fixed within an internal space of the case 11. Thecontrol button(s) or panel 16 and the optical system 17 may be disposedoutside the cause and/or on the external surface of the case 11.

Also, the pressing members 38 a, 38 b, and 38 c may be disposed withinand on the case 11 to support the optical system 17 and the photoniccrystal 33. For example, the pressing members 38 a, 38 b, and 38 c mayinclude a first pressing member 38 a which is disposed to partiallycontact a light-reflecting surface of the photonic crystal 33 to pressthe photonic crystal 33 and a second and a third pressing members 38 band 38 c for fixing and supporting the photonic crystal 33 so as not tobe deviated from the optical axis.

The first pressing member 38 a may be formed in a cylinder shape or apolygonal tube shape in which the optical system 17 may be disposedinside. Also, the first pressing member 38 a may have a portion whichprotrudes outwardly from the case 11 and configured to be slidableforward and backward with respect to the case 11.

The second pressing member 38 b is fixed within the case 11 and performsa role of supporting the photonic crystal 33 to not move in the opticalaxis direction.

The third pressing member 38 c performs a role of supporting thephotonic crystal 33 to not move in a direction perpendicular to theoptical axis and may be configured to surround at least a portion of alateral side of the photonic crystal 33. Here, the second pressingmember 38 b and the third pressing member 38 c may be integrally formed.In other embodiments, pressing members 38 b and 38 c may be separatedprovided.

In addition, within the first pressing member 38 a, the light source 12and the aperture 14 may be disposed. Although not shown in FIG. 7, thelight source 12 and the aperture 14 may be, for example, fixed on theoptical axis through a plurality of supporters connected to an internalwall of the first pressing member 38 a. The light source 12 may bedisposed within the first pressing member 38 a to emit light toward thephotonic crystal 33.

FIG. 7 shows that the aperture 14 is disposed between the light source12 and the optical system 17. However, the aperture 14 may be disposedanywhere between the photonic crystal 33 and the optical system 17 inother embodiments. In order not to block the light reflected from thephotonic crystal 33, the light source 12 and the aperture 14 may bedisposed on a non-focal plane of the optical system 17.

In this configuration, only light in a certain wavelength band of thelight emitted from the light source 12 is reflected by the photoniccrystal 33. The wavelength band of the reflected light may be selectedby adjusting a force by which the user presses the first pressing member38 a against an external object such as a light-sensing board, asdescribed in FIGS. 5A and 5B. The light reflected from the photoniccrystal 33 may reach the optical system 17 through the first pressingmember 38 a and may be projected toward the outside by the opticalsystem 17. Here, the internal wall of the first pressing member 38 a mayhave reflectivity in order to prevent light loss.

As described above, the light-emitting apparatuses 10, 20, 30, and 40may allow the user to freely select the color of the projected light byusing the photonic crystals 13 and 33 having a variable photonicbandgap. According to one embodiment, the user may continuously vary thecolor of the projected light within the visible light region accordingto a range of the photonic bandgap of the photonic crystals 13 and 33.Also, it is possible that the user may freely adjust the beam diameterof the projected light.

Therefore, the light-emitting apparatuses 10, 20, 30, and 40 may beused, for example, as an optical pen capable of allowing the user toselect a desired image color and a desired line thickness from the penitself. Also, the light-emitting apparatuses 10, 20, 30, and 40 may beused to provide a light of various colors not only as the optical penbut also as an optical pointer, an educational terminal, an electricalboard, etc.

In the aforementioned embodiments, the photonic bandgap of a photoniccrystal is discussed as outputting blue or red light. In otherembodiments, the phontonic bandgap may be adjusted to output additionalcolors of light. Also, the aforementioned embodiments are discussed asswitching between two colors of output light. In other embodiments, morethan two colors of light may controlled for output.

FIG. 8 is a schematic view illustrating a structure of a light-emittingapparatus according to another embodiment. In this embodiment, theapparatus outputs more than two colors of light using photonic crystal13 and a filter 80. The photonic crystal 13 is tuned to output twocolors of light (e.g., blue and red) when different control signals ormechanical pressures are applied, and the filter may be tuned to one ormore different wavelengths.

For example, the filter may be tuned, designed, or otherwise designed topass a combination of the light output from the photonic crystal 13 andanother wavelength of light. When the other wavelength of light isyellow and the photonic crystal outputs red light, the combined outputlight is orange. When the photonic crystal outputs blue light, thecombined output light is green.

In accordance with one embodiment, the filter may be a resonator whichis tuned to one color or which changes between two or more colors. Anexample of such a resonator is a metal-insulator-metal resonator. Whensuch a resonator is used, the resonator may be tuned to yellow when afirst voltage is applied and may be clearly transparent when anothervoltage is applied. In this case, four colors of light may be output:blue when the photonic crystal outputs blue and the resonator istransparent; red when the photonic crystal outputs red and the resonatoris transparent; green when the photonic crystal outputs blue and theresonator is set to yellow; and orange when the photonic crystal outputsred and the resonator is set to yellow.

The photonic crystal and resonator may be electronically controlled tooutput the different colors and/or mechanically controlled. In anelectronic control embodiment, a surface of the apparatus may include acontrol button which, when pressed repeatedly, causes the differentcolors of light to be output sequentially. In other embodiments,multiple buttons may be included, one for each color.

Instead of a resonator, another photonic crystal tuned to differentcolors (e.g., ones different from photonic crystal 13) may be used asfilter 80.

Also, instead of a photonic crystal, at least one embodiment may use aphotonic crystal fiber designed to output different colors of lightbased on electronic control signals and/or the application of mechanicalpressure. Examples of photonic crystal fibers include photonic bandgapfibers, holey fibers which use air holes in their cross-sections toseparate, block or pass light of certain wavelengths, hole-assistedfibers which guide light based on higher-index cores modified by thepresence of air holes), and so-called Bragg fibers made from concentricrings of multilayer film(s)).

Example embodiments having thus been described, it will be obvious thatthe same may be varied in many ways. Such variations are not to beregarded as a departure from the intended spirit and scope of exampleembodiments, and all such modifications as would be obvious to oneskilled in the art are intended to be included within the scope of thefollowing claims.

What is claimed is:
 1. A light-emitting apparatus comprising: a lightsource configured to emit light; a photonic crystal configured to passlight of different wavelengths based on the light emitted from the lightsource; and a projector configured to project the light which passesthrough the photonic crystal, the photonic crystal configured to beelectrically controlled to pass the different wavelengths of light. 2.The light-emitting apparatus of claim 1, further comprising: an apertureconfigured to control a beam diameter of the projected light; acontroller configured to control operation of at least one of thephotonic crystal or the aperture; and a input device configured toreceive a command to be sent to the controller.
 3. The light-emittingapparatus of claim 2, wherein the photonic crystal and the aperture arearranged along an optical axis between the light source and theprojector.
 4. The light-emitting apparatus of claim 1, furthercomprising: a first transparent electrode coupled to a light incidentsurface of the photonic crystal; and a second transparent electrodecoupled to a light emission surface of the photonic crystal, wherein afirst voltage difference between the first and second transparentelectrodes corresponds to a first wavelength of the differentwavelengths of light, and a second voltage difference between the firstand second transparent electrodes corresponds to a second wavelength ofthe different wavelengths of light.
 5. The light-emitting apparatus ofclaim 4, wherein the photonic crystal includes a colloid solvent, and aplurality of photonic crystal particles arranged within the colloidsolvent in a periodic structure, and the photonic crystal particles havea surface which is electrically charged such that a repulsive force isapplied therebetween.
 6. The light-emitting apparatus of claim 5,wherein the photonic crystal particles comprise particles of silica,polymethylmethacrylate (PMMA), poly-n-butylmethacrylate (PBMA), orcopolymer thereof.
 7. The light-emitting apparatus of claim 4, whereinthe photonic crystal comprises a transparent polymer which contracts orexpands based on the first and second voltage differences respectively;and a plurality of photonic crystal particles arranged within thetransparent polymer in a periodic structure.
 8. A light-emittingapparatus comprising: a light source configured to emit light; aphotonic crystal configured to pass light of different wavelengths basedon the light emitted from the light source; a projector configured toproject the light which passes through the photonic crystal; and adeflector configured to apply a pressure to cause the photonic crystalto change between contracted and expanded states, the photonic crystalhaving a photonic bandgap which varies according to the contracted andexpanded states of the photonic crystal, the photonic crystal configuredto output a first wavelength of the different wavelengths in thecontracted state and configured to output a second wavelength of thedifferent wavelengths in the expanded state.
 9. The light-emittingapparatus of claim 8, further comprising: an aperture configured toadjust a beam diameter of the projected light; a controller configuredto control operation of the aperture; and an input device configured toreceive a command to be sent to the controller.
 10. The light-emittingapparatus of claim 9, wherein the aperture and the photonic crystal aresequentially arranged along an optical axis between the light source andthe projector.
 11. The light-emitting apparatus of claim 8, wherein thedeflector comprises: a first surface configured to press the photoniccrystal; a second surface configured to prevent movement of the photoniccrystal in a direction of an optical axis; and a third surfaceconfigured to prevent movement of the photonic crystal in a directioncrossing the optical axis.
 12. The light-emitting apparatus of claim 11,further comprising: a case, wherein the first surface has a portionwhich protrudes outwardly from the case to contact an external objectand configured to slide in forward and backward directions with respectto the case, and wherein, when the first surface contacts the externalobject, the first surface presses against the photonic crystal to causethe photonic crystal to pass from the expanded state to the contractedstate.
 13. The light-emitting apparatus of claim 8, wherein the photoniccrystal comprises: a transparent elastic material which changes betweenthe contracted state and the expanded state based on a pressure; and aplurality of photonic crystal particles arranged within the transparentelastic material at a periodic structure.
 14. A light-emitting apparatuscomprising: a light source configured to emit light; a photonic crystalconfigured to reflect light of different wavelengths based on the lightemitted from the light source; a projector configured to project thelight reflected by the photonic crystal; and a light guide disposedbetween the photonic crystal and the projector to transmit light emittedfrom the light source to the photonic crystal and to transmit the lightreflected by the photonic crystal to the projector, the photonic crystalhaving a variable photonic bandgap which is electrically controlled toadjust the wavelength of the reflected light.
 15. The light-emittingapparatus of claim 14, further comprising: an aperture configured toadjust a beam diameter of the projected light; a controller configuredto control operation of at least one of the photonic crystal or theaperture; and an input device configured to receive a command to betransmitted to the controller.
 16. The light-emitting apparatus of claim15, wherein the photonic crystal, the aperture, the light guide, and theoptical system are sequentially arranged along an optical axis, and thelight source is offset from the optical axis and disposed toward anentrance to the light guide.
 17. The light-emitting apparatus of claim16, further comprising: a beam splitter disposed at an entrance to thelight guide, wherein the beam splitter is configured to reflect lightemitted from the light source toward the photonic crystal and to passthe light reflected by the photonic crystal.
 18. The light-emittingapparatus of claim 14, further comprising: a first transparent electrodedisposed on a light incident surface of the photonic crystal, and asecond transparent electrode disposed on a light emission surface of thephotonic crystal.
 19. The light-emitting apparatus of claim 18, whereinthe photonic crystal includes a colloid solvent, and a plurality ofphotonic crystal particles arranged within the colloid solvent in aperiodic structure, the photonic crystal particles having a surfacewhich is electrically charged such that a repulsive force is appliedtherebetween.
 20. The light-emitting apparatus of claim 19, wherein thephotonic crystal particles comprise particles of silica,polymethylmethacrylate (PMMA), poly-n-butylmethacrylate (PBMA), orcopolymer thereof.
 21. The light-emitting apparatus of claim 14, whereinthe photonic crystal comprises: a transparent polymer which expands andcontracts based on electrical stimulus; and a plurality of photoniccrystal particles arranged within the transparent polymer in a periodicstructure.
 22. A light-emitting apparatus comprising: a light sourceconfigured to emit light; a photonic crystal configured to reflect lightof different wavelengths based on the light emitted from the lightsource; a projector configured to project the light reflected by thephotonic crystal; and a deflector configured to apply pressure forcausing the photonic crystal to change between contracted and expandedstates, the photonic crystal having a photonic bandgap which variesbetween the contracted and expanded states to adjust the wavelength ofthe reflected light.
 23. The light-emitting apparatus of claim 22,further comprising: an aperture configured to control a beam diameter ofthe projected light; a controller configured to control operation of atleast one of the photonic crystal or the aperture; and an input deviceconfigured to receive a command to be sent to the controller.
 24. Thelight-emitting apparatus of claim 22, wherein the deflector comprises: afirst surface configured to press the photonic crystal; a second surfaceconfigured to prevent movement of the photonic crystal in a direction ofan optical axis; and a third surface configured to prevent movement ofthe photonic crystal in a direction crossing to the optical axis. 25.The light-emitting apparatus of claim 24, further comprising: a case,wherein the first surface has a portion which protrudes outwardly fromthe case to contact an external object and is configured to slideforward and backward with respect to the case, and wherein, when thefirst surface slides in the backward direction, the first surfacepresses against the photonic crystal.
 26. The light-emitting apparatusof claim 25, wherein the first surface has a cylinder shape or apolygonal tube shape, and the light source and aperture are disposedadjacent the first surface.
 27. The light-emitting apparatus of claim22, wherein the photonic crystal comprises: a transparent elasticmaterial which changes between expanded and contracts states based on apressure; and a plurality of photonic crystal particles arranged withinthe transparent elastic material at a periodic structure.